The temperature inside of a compressed gaseous fuel gas tank will change during fuel supply and during filling. Also, if fuel is supplied to the engine or to the fuel cell, the temperature of the gas decreases. These effects are due to fundamental laws of thermodynamics. However such tanks have temperature thresholds defined for the compressed gaseous fuel storage system and once the upper or lower limits are exceeded, it is necessary to remove the tanks from service. Current art provides for supervising the gas temperature in the tank using electric temperature sensor(s) together with an electric supervision system. Embodiments herein described provide for advantages over current systems.
Embodiments herein described do not require a constant supply of electricity. Current systems require electricity in order to enable the supervision. The current embodiments provide advantages in situations such as when the vehicle is parked. With current systems the available electricity is limited as it needs to be provided from a limited energy reservoir (e.g. from a rechargeable energy system). Additionally, with current systems, employing an electrical temperature supervision system involves employing vehicle data acquisition, and the energy consumption to perform such operations can be significant. Therefore, if the vehicle is not operated, the temperature supervision is limited to a time interval of currently several minutes. The embodiments herein described address this need in the art. Such embodiments provide constant supervision of temperature, thus increasing efficiency and limiting unnecessary decommissioning of storage systems.
Developing a more energy efficient supervision system beyond currently available systems is desirable, but would still only slightly extend supervision times. Therefore it is desirable to have a passive system in place which permanently stores the information once the tank temperature goes above or below a provided range.